CN1036787A - The method for thermal cracking of residual hydrocarbon oils - Google Patents

Abstract

The thermal cracking method of residual hydrocarbon heavy oil through the following steps:

1) Send heavy residual hydrocarbon oil and a kind of synthesis gas into the thermal cracking zone, the combined The resulting gas has a temperature high enough that the temperature of the thermal cracking zone passes through the direct The heat exchange is kept at 420-850°C,

2) separation of cracked products into (a) a gas, (b) a or various fractions and (c) a cracked residue,

3) Separating the cracked residual oil into one or more asphaltene-poor Heavy hydrocarbon oils and one or more heavy hydrocarbon oils rich in asphaltenes,

4) Gasify the above-mentioned heavy hydrocarbon oils under the participation of oxygen and steam to produce generate syngas, and

5) Apply syngas from step 4 as syngas to step Step 1.

Description

The invention relates to a method for thermal cracking of residual hydrocarbon oil.

Residue oils can be obtained by distilling crude oil at atmospheric pressure, producing a straight-run fraction and a raffinate also known as "long boiling raffinate". This long boiling raffinate is usually distilled under reduced pressure to produce one or more so-called "vacuum cuts" and a raffinate also known as a "short boiling raffinate". There have been many research topics aimed at converting not only residual oils but also other residual oils, such as those obtained from oil sands and shale oil, into more valuable products.

"Wissenschaft und Technik, Erdoel und Kohle-Erdgas-Petro-chemie vereinit mit Brenn -fchemie" 36, October 1983 pp. 457-461 Paper dealing with hydrothermal cracking of residual hydrocarbon oils. An oil sands heavy oil cracked in this manner separates a gaseous fraction containing hydrocarbon oils having 1 to 4 carbon atoms per molecule and a liquid residual fraction by forming cracked products therefrom. The liquid residual fraction contained 70% by weight of a fraction having an end boiling point of 592°C. The tests were carried out by preheating oil sands heavy oil to a temperature of 375°C, preheating hydrogen to a temperature of 1200°C and introducing these preheated feeds into a reactor, the hydrogen temperature being high enough to provide thermal cracking required heat.

Japanese Patent Application Laid-Open No. 62-96589 relates to a process in which a mixture of heavy hydrocarbon oil, hydrogen and carbon-containing fines is cracked, and the cracked products are separated into a gas, a light oil, a middle distillate and Cracked residual oil which has been deasphalted by forming a deasphalted oil and a more asphaltene-rich hydrocarbon fraction by forming synthesis gas in the presence of oxygen and steam In gasification, carbon-containing fines particles are separated from the synthesis gas, and the separated particles are recycled to thermal cracking. The presence of hydrogen in the thermal cracking zone reduces the difficulties presented by the formation of carbonaceous products in thermal cracking and the production of oils with high stability and low olefin content. In this known method the material to be thermally cracked is heated to the cracking temperature indirectly, that is to say by means of heat transfer through the walls of the material. Its disadvantage is that carbonaceous deposits may gradually accumulate on the inner wall through the formation of a mixture to be cracked, which leads to a reduction in the heating continuous operation time of the furnace. This disadvantage is particularly serious where high conversion of heavy hydrocarbon oils is the aim. Another disadvantage is the inability to remove metal particles and ash normally present in the synthesis gas. Consequently, the concentration of metals and ash will increase.

It is an object of the present invention to eliminate the disadvantages of indirect heating of residual hydrocarbon oils to thermal cracking temperatures.

Another object is to reduce the concentration of metal particles and ash in the process.

Another object is to use hydrogen in an easily available form.

Therefore, the present invention provides a kind of thermal cracking method of residual hydrocarbon oil, and this method comprises the following steps:

Step 1: sending residual hydrocarbon oil and a synthesis gas to the thermal cracking zone, the synthesis gas having a temperature high enough to keep the temperature of the thermal cracking zone at 420-850°C by direct heat exchange;

Step 2: separating the cracked product from Step 1 into (a) a gaseous fraction containing synthesis gas, (b) one or more hydrocarbon fractions and (c) cracked residue;

Step 3: separating the cracked residual oil from Step 2 into one or more relatively asphaltene-depleted heavy hydrocarbon oils and one or more asphaltene-rich heavy hydrocarbon oils;

Step 4: Gasifying the one or more relatively asphaltene-depleted heavy hydrocarbon oils from Step 3 in the presence of oxygen and steam with concomitant formation of synthesis gas; and

Step 5: The syngas from step 4 is applied to step 1 as syngas.

The residual hydrocarbon oil is directly contacted with the hot synthesis gas in step 1, thereby providing the heat for thermal cracking and eliminating the disadvantage of indirect heating of the residual hydrocarbon oil to the cracking temperature. Effective contact is an important measure to reduce the formation of carbon-containing products; by providing a large oil-gas interface in the thermal cracking zone, for example, using a sprayer into which residual hydrocarbon oil and hot synthesis gas are respectively introduced, effective oil-gas contact can be performed.

The temperature in step 1 is an important variable in thermal cracking. Desirable Thermal Cracking Effect, That is, Reduction of Molecular Weight and Viscosity of Residual Hydrocarbon Oil 1948, Chapter 3 Knows that the difference in cracking rates of large and small molecules increases at lower temperatures and therefore the resulting desirable effect will be greater. At very low temperatures, that is to say below 400° C., the cracking rate decreases to uneconomically small values and large amounts of ethylenically unsaturated products are formed. At very high temperatures, that is to say above 850°C, a large amount of gaseous and carbonaceous products will be formed and a small amount of hydrocarbon fraction will be formed in step 2, while a small amount of heavy hydrocarbons which are less asphaltene-depleted will be produced in step 3 oils. In order to achieve more fractions in step 2 and more asphaltene-poor heavy hydrocarbon oils in step 3, and the heavy hydrocarbon oils contain a relatively low amount of ethylenically unsaturated products, the temperature of the thermal cracking zone is preferably maintained at 420- In the range of 645°C, preferably in the range of 460-550°C.

The residual hydrocarbon oil and synthesis gas are sent to a thermal cracking zone where a reaction mixture is formed which is allowed a certain normal residence time. This normal residence time is another important variable in thermal cracking. Generally speaking, the normal residence time is formulated according to the temperature. The thermal cracking in step 1 is preferably carried out at a normal residence time in the range of 1 second to 10 minutes, preferably in the range of 10 seconds to 10 minutes. At residence times as low as 1 second, thermal cracking will not proceed adequately, while residence times above 10 minutes increase the amount of gas and carbonaceous products and produce small hydrocarbon fractions in step 2 and small amounts in step 3 Heavy hydrocarbon oils that are poor in asphaltenes. In the present invention the normal residence time is determined according to V:F, where "V" is the volume of the thermal cracking zone and "F" is the volume of residual hydrocarbon oil input to the thermal cracking zone per unit time.

The pressure range in step 1 is preferably 2-50 bar, especially 3-10 bar, in order to provide a large oil-gas interface in the thermal cracking zone and to increase the asphaltene-depleted heavy hydrocarbon oil in step 3 Formation.

Examples of residual hydrocarbon oils which can be used in step 1 according to the invention are long boiling range residual oils, short boiling range residual oils, residual oils obtained by distillation of hydrocarbon mixtures formed without hydrothermally cracking hydrocarbon oils and residual oils derived from oil sands or shale oil. Residual oils may, if desired, be blended with a heavy distillate fraction, such as a recycle oil obtained by catalytic cracking of hydrocarbon oil fractions, or with a heavy hydrocarbon oil obtained by extraction from a residuum oil. Hydrocarbon oil blend.

The cracked product from step 1 is separated in step 2 into a gaseous fraction, one or more hydrocarbon fractions and a cracked residue. This can be accomplished, for example, by withdrawing gases from the top of the thermal cracking zone and cracked residues from the bottom of the thermal cracking zone. The gas exiting the top is separated by means of atmospheric distillation into (a) a gaseous fraction containing synthesis gas, hydrocarbons with 1 to 4 carbon atoms per molecule and hydrogen sulphide, if to be gasified in step 4 The more asphaltene-rich hydrocarbon fractions of (b) a gasoline fraction, (c) a kerosene fraction, (d) a gas oil fraction and (e) a small amount of a residual oil if the more asphaltene-rich hydrocarbon fractions also contain sulfur. This small amount of resid can be mixed with the cracked resid obtained in step 2. Hydrogen sulfide may be removed from the gaseous fraction by any suitable conventional technique. After removal of hydrogen sulfide, the gaseous fraction can be separated into synthesis gas and hydrocarbons by conventional separation techniques. This synthesis gas can be reused in step 1, if desired, after enrichment with hydrogen, for example, either as a fuel gas or as a gas for driving power generation.

The cracked resid from step 2 contains heavy hydrocarbon oils, asphaltenes, suspended carbonaceous particles and, if any, heavy metals.

According to a preferred embodiment of the present invention, the cracked residual oil from step 2 is separated in step 3 into one or more asphaltene-poor heavy hydrocarbon oil fractions and a relatively asphaltene-rich heavy hydrocarbon oil fraction by means of negative pressure distillation. residual hydrocarbon oil. This distillation is conveniently a flash distillation and can be carried out in one or more columns or flashers.

According to another preferred embodiment of the present invention, the cracked residual oil from step 2 is contacted with an extraction solvent in step 3, whereby an extraction phase containing heavy hydrocarbon oils depleted in asphaltenes and A heavy hydrocarbon oil extraction residue rich in asphaltenes. The extraction solvent is preferably an alkane or a mixture of alkanes, most preferably propane, butane, isobutane and/or pentane. Preferentially subjected to the role of pentane. The extraction methods described above are well known prior art. Extraction phase and extraction residue, that is, heavy hydrocarbon oil rich in asphaltene can be separated by gravity settling method, and the separated extractive phase can be separated into extractant and heavy hydrocarbon oil poor in asphaltene by means of distillation. hydrocarbon oil.

The asphaltene-rich hydrocarbon fraction also contains suspended particles of carbonaceous products and, if at all, heavy metals such as vanadium and nickel. This fraction is gasified in step 4 under the addition of oxygen and steam with the concomitant production of a synthesis gas containing carbon monoxide and hydrogen as main components, this gasification being a partial oxidation. Hydrogen is therefore available and does not need to be separated from carbon monoxide. Syngas contains carbonaceous product particles and ash and generally heavy metals.

The gasification of step 4 can be carried out, for example, at a weight ratio of oxygen to hydrogen in the range of 0.5-1.5 and a weight ratio of steam to hydrocarbon fraction in the range of 0.2-1, both of which vary with the molecular composition of the fuel and the gasification process. depends on the melting temperature. These two weight ratios also determine the amount of carbonaceous product formed. Gasification can be carried out in a certain pressure range, for example 1-100 bar, and a certain pressure stage  Lu  ~ 000-1600 ° C.

Metal particles and ash in the syngas from step 4 are preferably removed from the syngas selectively relative to carbonaceous product particles in the syngas before the gas is applied to step 5 . This has the advantage that the carbonaceous particles ultimately present in the relatively asphaltene-rich heavy hydrocarbon oil are separated in step 3 and subsequently gasified in step 4. It is a convenient advantage of the present invention that the carbonaceous product particles do not need to be removed as waste. Selective removal can be performed based on the size and specific gravity difference between carbon-containing product particles and metal particles and ash. Carbonaceous product particles generally have a smaller size and specific gravity, while metal particles and ash generally have a larger size and specific gravity. This separation can be performed, for example, with a cyclone separator. Such separation of metals and ash can be used to recover these metals.

The synthesis gas should have a temperature high enough to maintain the temperature of the thermal cracking zone at 420-850°C. An advantageous advantage of the present invention is that waste heat can generally be used in the synthesis gas according to this need. Therefore, the heat in the syngas from step 4 can usually be released from the syngas, preferably by means of indirect heat exchange using a cooling medium such as water. This offers the possibility of generating higher pressure steam and controlling the temperature of the thermal cracking zone. On the other hand, the synthesis gas is cracked into two parts, one part is used in step 1 to keep the temperature of the thermal cracking zone in the range of 420-850°C, and the other part is used for any other suitable purpose. For example another part may be fired in a boiler for generating electricity.

The more asphaltene-rich hydrocarbon fraction separated in step 3 may be used for any suitable purpose. For example, when the hydrocarbon fraction has a low specific gravity, viscosity and Conradson ash content and contains no or very low levels of carbonaceous particles, it is quite suitable as a blending component for industrial fuels. On the other hand, it can be catalytically cracked or hydrocracked to produce gasoline and kerosene fractions, or it can be recycled to the thermal cracking zone of step 1 for thermal cracking of light hydrocarbon oil fractions.

The invention is explained in more detail below with reference to the accompanying drawings, in which Figures 1 and 2 each represent a simplified flow chart of the method of the invention. Auxiliary equipment such as heat exchangers and valves are not shown in the figures. Figure 1 shows a specific scheme of distilling cracked residual oil under negative pressure, while Figure 2 shows a specific scheme of deasphalting cracked residual oil.

Referring to FIG. 1 , heavy hydrocarbon oil enters thermal cracker 3 through pipelines 1 and 2 . Syngas enters thermal cracker 3 via line 4 (step 1).

A gaseous phase and a cracked residue are discharged from the thermal cracker 3 through lines 5 and 6, respectively. The gaseous phase passes through line 5 into distillation column 7, in which the gaseous phase is separated at atmospheric pressure into an overhead fraction containing synthesis gas, a full-range naphtha fraction, a gas oil fraction and a bottoms fraction, the fractions being It is withdrawn from the distillation column 7 via lines 8, 9, 10 and 11 (step 2).

The cracked residual oil is sent to a vacuum distillation column 13 through pipelines 6 and 12, in which the cracked residual oil is separated under negative pressure into a vacuum top fraction, one or more vacuum fractions and an asphaltene-containing bottom fraction, They are removed from the vacuum distillation column 13 through lines 14, 15 and 16, respectively (step 3). The overhead and vacuum fractions are substantially free of asphaltenes, while the bottoms fraction contains carbonaceous product particles.

The fraction containing asphaltenes is sent via line 16, a pump 17 and line 18 to a gasifier 19 where it is oxidized, and steam is sent to gasifier 19 via line 20. The synthesis gas produced in the gasifier 19 is discharged from the gasifier via line 21 (step 4).

The synthesis gas is passed through line 21 to a separator 22 from which metal particles and ash are selectively removed. Synthesis gas, substantially free of metal particles and ash, but still containing carbonaceous product particles, exits separator 22 through line 23 and enters a waste heat boiler 24 in which residual heat is removed from the synthesis gas. The reduced temperature syngas is drawn from the waste heat boiler 24 through line 4 and fed to the thermal cracker 3 as described above (step 5).

The metal particles and ash separated from the synthesis gas in separator 22 are discharged from the separator through line 25 . Water is fed into the waste heat boiler 24 through line 26 and high pressure steam is discharged from the boiler through line 27 .

In this case, the vacuum middle distillate conveyed via line 15 is directed partly via line 28 to a predetermined external treatment and partly recirculated via line 29 into line 2 to enhance the formation of the full Range naphtha fraction and gas oil fraction. Alternatively, the entire vacuum middle distillate can be withdrawn from line 15 via line 28 . The latter is usually preferred.

The bottoms fraction conveyed via line 11 is fed into line 12 by means of a raw material 30 and line 31 .

Reference numerals referring to the same parts in Figures 1 and 2 are the same.

Referring to Fig. 2, the cracked residual oil from thermal transporter 3 is sent through line 6 to a solvent deasphalting unit 50 where it is separated into a deasphalted oil substantially free of carbonaceous product particles and a deasphalted oil containing Fractions of asphaltene and carbonaceous product particles, which are removed from unit 50 through lines 15 and 16 respectively (step 3), carbonaceous products produced by gasifier 19 and thermal cracker 3 .

The deasphalted oil discharged through line 15 is sent partly via line 28 to a predetermined external treatment and partly recirculated into line 2 via line 29 to increase the formation of the full range naphtha fraction and Gas oil fraction. On the other hand, the entire deasphalted oil from line 15 can be discharged through line 28 . The latter is usually preferred.

Example 1

This embodiment is carried out with reference to FIG. 1 . The heavy hydrocarbon oil fed through line 1 is a short boiling residue with the following properties:

Specific gravity 25℃/25℃ 1.028

Viscosity 150℃ 154cS

Initial boiling point ℃ 520

Vanadium content ppm 135.8

Nickel content ppm 43.3

Sulfur content % by weight 5.30

Conradson residual ash weight % 21.7

C ₅ - Asphaltenes wt% 19.9

The abbreviation "ppm" means parts per million by weight. Thermal cracker 3 is a cylindrical vessel operated at 475°C, 0.6 bar pressure and a normal residence time of 3 minutes. The gasifier 19 was operated at 1400° C., a pressure of 30 bar and a residence time of 5 seconds, while the distillation column 14 was operated at a pressure of 0.013 bar. High pressure steam is discharged through line 27.

Get the following all material comparison:

input Output

Pipeline kg/hour Pipeline kg/hour

1 Short boiling range residual oil 125.0 8 Light hydrocarbons and synthesis gas 116.6

20 oxygen 37.9 9 naphtha, C ₅ -165°C 13.3

20 Steam 28.4 10 Gas oil, 165-370℃ 12.1

28 Vacuum flash fraction, 370-550°C 48.3

25 Metal solid particles and ash 1

191.3 191.3

The material comparison near thermal cracker 3 is as follows:

input Output

Pipeline kg/hour Pipeline kg/hour

4 112.5 5 142.0

2 125.0 6 95.5

237.5 237.5

The material comparison near the vacuum distillation tower is as follows:

input Output

Pipeline kg/hour Pipeline kg/hour

12 95.5 14 negligible

15 48.25

16 47.25

95.5 95.5

Some properties of the flashed fraction in line 28 and the asphaltene-containing fraction in line 16 are as follows:

Vacuum Flash Distillate Asphaltene Containing Fraction

Specific gravity 25℃/25℃ 1.116 1.015

Viscosity cS 30.2 at 100°C 779 at 200°C

Vanadium content ppm 0.4 335

Nickel content ppm 0.6 113

Sulfur content % by weight 4.0 6.1

Conradson charcoal weight % 0.8 56.2

C ₅ - Asphaltenes wt% 0.02 63.6

The vacuum flashed fraction was free of carbonaceous product particles. Composition of the asphaltene-containing fraction removes carbon-containing product particles.

The gas removal carbonaceous product particles in line 4 contain the following composition (at 20°C, mole %):

CO 46.6 CO ₂ 3.4 H ₂ S 1.4

H ₂ 41.5 H ₂ O 6.5 N ₂ 0.6

Example 2

This embodiment is carried out according to FIG. 2 . The heavy hydrocarbon oil fed through line 1 was the same short boiling raffinate as used in Example 1. Thermal cracker 3 was operated at 475°C, a pressure of 6.0 bar and a cold oil residence time of 3 minutes. The gasifier 19 was operated at 1400° C., a pressure of 30 bar and a residence time of 5 seconds. Extraction column 50 is a rotating circular contactor operated isothermally at 185°C and 40 bar pressure, using n-pentane as the extraction solvent. An extraction solvent was added at a feed weight ratio of 2.0 using a 100 rpm rotator.

Get the following comparison of all materials:

input Output

Pipeline kg/hour Pipeline kg/hour

1 Short boiling range residue 125.0 8 Light hydrocarbons and synthesis gas 72.4

20 Oxygen 23.0 9 Naphtha, C ₅ -165°C 13.3

20 Steam 17.4 10 Gas oil, 165-370℃ 12.1

28 deasphalted oil 66.8

25 Metal solid particles and ash 0.8

165.4 165.4

The material comparison near thermal cracker 3 is as follows:

input Output

Pipeline kg/hour Pipeline kg/hour

4 68.3 5 97.8

2 125.0 6 95.5

193.3 193.3

The material comparison near the solvent deasphalting unit 50 is as follows:

input Output

Pipeline kg/hour Pipeline kg/hour

12 95.5 15 66.8

16 28.7

95.5 95.5

The gas in the pipeline 4 for removing carbonaceous product particles contains the following composition (at 20° C., mole %):

CO 48.2 CO ₂ 3.1 H ₂ S 1.6

H ₂ 40.9 H ₂ O 6.0 N ₂ 0.2

Certain properties of the deasphalted oil in line 28 and the asphaltene-containing fraction in line 16 are as follows:

Deasphalted Oils Asphaltene Fraction

Specific gravity 25℃/25℃ 1.007 1.221

Viscosity cS 65 at 100°C 75110 at 200°C

Vanadium content ppm 26.5 530

Nickel content PPm 12.9 159

Sulfur content % by weight 4.2 7.1

Conradson charcoal weight% 10.4 70.7

C ₅ - Asphaltene wt% 5.7 92.7

Composition of the asphaltene-containing fraction removes carbon-containing product particles. Deasphalted oils are free of carbonaceous product particles.

Claims (13)

1, a kind of method of thermally splitting residual hydrocarbon oils comprises the following steps:

Step 1: send residual hydrocarbon ils and a kind of synthetic gas to the thermally splitting district, this synthetic gas has sufficiently high temperature, so that the temperature in thermally splitting district remains on 420-850 ℃ by direct heat exchange;

Step 2: will be separated into (a) a kind of gaseous fraction that contains synthetic gas from the crackate of step 1, (b) one or more hydrocarbon-fractions and (c cracking Residual oil;

Step 3: will be separated into one or more from the cracking Residual oil of step 2 poorlyer has bitum heavy hydrocarbon oils and one or more to be rich in bitum heavy hydrocarbon oils;

Step 4: gasification is rich in bitum heavy hydrocarbon oils from one or more of step 3 under aerobic and steam are participated in, and follows the formation synthetic gas; And

Step 5: will be applied in the step 1 as synthetic gas from the synthetic gas of step 4.

2, a kind of according to the process of claim 1 wherein that the thermally splitting of step 1 carries out in 420-645 ℃ scope.

3, a kind of method according to claim 2, wherein the thermally splitting of step 1 is carried out in 460-550 ℃ scope.

4, a kind of according to arbitrary described method in the aforesaid right requirement, wherein step 1 is carried out in 3-10 bar pressure scope.

5, a kind of according to each described method in the aforesaid right requirement, wherein the thermally splitting of step 1 is carried out in 1 second to 10 minutes normal residence time scope.

6, a kind of method according to claim 5, wherein the thermally splitting of step 1 is carried out in 10 seconds to 10 minutes normal residence time scope.

7, a kind of require according to aforesaid right in each described method, wherein from the heat in the synthetic gas of step 4 in gas application before the step 5, by indirect heat exchange by heat-eliminating medium from wherein discharging.

8, a kind of require according to aforesaid right in each described method, wherein from metallic particles in the synthetic gas of step 4 and ash content, before the step 5, optionally from ground gas, remove with respect to the carbonaceous products particle in this gas application.

9, a kind of require according to aforesaid right in each described method, wherein utilizing the vacuum distillation method to be separated into one or more in step 3 from the cracking Residual oil of step 2 poorlyer has bitum heavy-hydrocarbon oil cut and a kind ofly is rich in bitum heavy residual hydrocarbon ils.

10, a kind of according to each described method among the claim 1-8, wherein send step 3 to a kind of extractant, follow to form a kind of contain poorer have bitum heavy-hydrocarbon oil extracting phase and a kind of extracting Residual oil that is rich in bitum heavy-hydrocarbon oil that contains from the cracking Residual oil of step 2.

11, a kind of method according to claim 10, wherein extractant is propane, butane, Trimethylmethane and/or pentane.

12, a kind of method according to claim 1 is described according to following embodiment basically.

13, hydrocarbon oils can obtain at any time by each described method in requiring according to aforesaid right.

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